Rhizina undulata

Rhizina undulata, commonly known as the doughnut fungus or the pine firefungus, is a species of fungus in the family Rhizinaceae. The fruit bodies of the fungus are dark purple brown with a bright yellow margin, crust-like and attached to the growing surface by numerous root-like yellow rhizoids. R. undulata has a cosmopolitan distribution, and commonly occurs on clearings or burned areas throughout central and northern Europe, North America, northern Asia, and southern Africa. It is parasitic on conifer seedlings, and has caused considerable damage to tree plantations worldwide.